The present invention relates to bread products having improved keeping qualities containing high levels of non-fat dry milk that substantially increase the quantity and quality of the bread's protein and calcium content. In particular, the present invention relates to bread products having improved keeping qualities, based upon flours having wheat protein contents of about 10% to about 17% by weight and containing heat treated non-fat dry milk in amounts of 24% to 48% by weight per 100 parts of flour.
Bread and milk are basic foods for much of the Western world. The amino-acid makeup of their individual proteins are complimentary and when combined in the correct proportions produce an over-all amino acid pattern similar to the 1973 recommended standard for protein quality of the Food Administration Organization (FAO) of the World Health Organization (WHO). Although bread or bread products are universally eaten, milk is consumed less consistently throughout society. Its consumption is particularly a problem in growing children, adolescent girls and adult women, groups where nutritionally complete proteins and calcium, provided by milk, are essential to bone development and maintenance.
The incorporation of milk usually as non-fat dry milk (NFDM) into bread can enhance the nutritional value of the final product, due to its content of casein and the whey proteins. However, U.S. Pat. No. 3,411,919 to Glabe discloses that these proteins, particularly the whey proteins, have a deleterious effect on bread structure, decreasing loaf volume and creating a dense unsatisfactory crumb. This necessitates the use of a NFDM which has been specially heat treated to denature the whey proteins. Heat treated NFDM is known in the art as "high heat" NFDM, which is described in U.S. Pat. No. 4,395,426 to Fan as milk that has been subjected to temperatures higher than normal pasteurization temperatures prior to drying so as to partially denature the milk proteins.
As noted in U.S. Pat. No. 4,395,426, "high heat" NFDM is conventionally used in yeast leavened baked goods. Even with high heat treatment it is generally accepted that the amount of NFDM should not exceed 8.2%, and usually not more than 6%, based upon the flour weight if satisfactory loaf volume is to be maintained, as disclosed by "Baking Production Technology," American Institute of Baking, Baltimore, Md., Conference of Nov. 7-9, 1988. This limits the amount of NFDM which can be incorporated into bread to about 23 g or 240 cc (8 ounces) skim milk equivalent in a standard loaf (454 g or 1 lb.). Considering 6 slices of bread (150 g) as an average daily consumption, this amount of added milk supplies only 6% of the recommended daily allowance (RDA) of protein and 10% calcium, relatively insignificant amounts of these nutrients.
U.S. Pat. No. 3,411,919 discloses that low quantities of NFDM in bread dough detracts substantially from the flavor of the resulting baked bread, as well as from its crust color, crumb texture and quality, particularly in the "no-time" process, a straight dough method with a fermentation time of one hour or less and the "continuous-mix" process, both of which sacrifice flavor for a shortened fermentation time. However, in these methods, once levels exceed 1% of the flour weight, there occurs a significant reduction in bread volume and deterioration of loaf shape, with weakened side walls. At the same time, levels of NFDM of less than 3% based upon flour weight will have little effect on the flavor of the finished product.
Andt, U.S. Pat. No. 3,271,164, discloses a continuous process of bread making in which there is added to the dough about 4% of NFDM from about 0.1% to 0.9% karaya gum and from about 0.02% to about 0.1% of a material selected from algins and carrageenans, all percentages being by weight of the flour. The aforementioned U.S. Pat. No. 3,411,919, describes a continuous-mix bread containing NFDM in amounts from 2-6% of the flour weight in which the loaf volume, shape and structural strength, ordinarily weakened by NFDM, are improved through the incorporation of 0.1% to 1.0% hydroxylated phosphatide, and 0.01% to 0.15% of carrageenan extract by flour weight. Although this amount of NFDM addition exceeds the accepted upper limit of 1% in the continuous-mix process, it is still a relatively small amount of milk and an insignificant contribution to the nutritional value of the bread.
The aforementioned Fan, U.S. Pat. No. 4,395,426, discloses a dry mix process for preparing bread without a kneading step, which bread contains in addition to other ingredients about 0.5 to 1.5 parts by weight per 100 parts of flour of a propylene glycol alginate and about 2 parts to 10 parts of a gum member by weight per 100 parts selected from karaya gum, guar gum, xanthan gum, high viscosity carboxymethyl cellulose, high viscosity carrageenan gum and mixtures thereof. The bread optionally contains 1 to 10 parts of high heat non-fat dry milk solids (NFDM).
Dotsenko et als., Pishchevaya Primyshlennost, 1, 32-33 (1987), using NFDM in amounts from 10-15%, based on the wheat flour weight, together with monoglyceride esters of diacetyl tartaric acid and the multi-enzyme complex MFK-KhP to hydrolyze the NFDM, showed improved rheological properties and binding capacities for the resulting doughs. There were no descriptions of bread products made from these doughs.
Before the process of staling was understood as it is today, the dryness associated with staled crumb of baked goods led to the use of hydrocolloidal vegetable gums as humectants or moisturizers. These agents take-up and hold water in amounts many times their own weight. As an example, the uptake of water by alginates is 26 cc/g in contrast to 1 cc/g for gluten and 0.4 cc/g for undamaged starch. It should be exphasized that these agents are not to be considered anti-stalants even though Andt calls the mixture of karaya and algins and/or carrageenans described above an additive to retard staling. Loaves treated with 0.5% of the additive showed a greater softness initially and after 96 hours when compared to control bread. However, the rate of firming, an index of staling, was similar in both groups.
Others claiming improvements in keeping qualities from hydrocolloidal vegetable gums due to moisture retention and softness include: Curtner, U.S. Pat. No. 1,534,783, Epstein, U.S. Pat. No. 1,964,940, and Ament, U.S. Pat. No. 2,158,392. Fiske, U.S. Pat. No. 1,657,116, describes a composition of gum tragicanth, 3.0%, and iodic acid, 0.0175%, based upon 100 lb of a bread flour mixture as a bread volume enhancer. Similarly, Dubois, U.S. Pat. No. 3,219,455, describes a bread additive comprising about 20-30 parts vital wheat gluten, 3-5 parts hydrophilic colloidal (carboxymethylcellulose) and 0.01-0.025 parts of an oxidizing agent (potassium bromate) based upon 1000 parts of bread flour which has the property of increasing bread volume and compressibility of breads made from said flours. Although the compressibility of loaves made with the additive is greater at 96 hours than control samples, the rate of firming of the additive containing groups is equal to or greater than the controls.
Although NFDM has beneficial effects on bread flavor and appearance, when used in proper amounts, there have been no reports that such additions alone or in combination with other ingredients delay the onset of bread staling or increase its keeping time.